The present invention relates to the provision of accurate high frequency signals which are capable of being adjusted and, more particularly, to phase or time adjustment means for adjusting such high frequency signals by very small increments and in very precise amounts and to a method for making such small, high precision time or phase delays.
The primary application for the instrument of the present invention reside in those fields in which precise time and frequency signals are required and wherein such precise high frequency signals require adjustment. Some applications for adjustment means are cesium clocks which require periodic adjustment due to the fact that they are subjected to drift, as well as other systems such as Loran "C" stations, Omega stations and G.P.S. Systems. A micro time and phase stepper may, in fact, be used to great advantage in any system requiring a precision phase or time controller. As one example, micro time and phase controllers may be advantageously employed in earth stations utilized in satellite communication networks.
Although at least one prior art device exists for providing micro time and phase control, such device has been found to have some significant shortcomings which render its use impractical in certain applications, some of the disadvantages of the prior art device including:
I. the conventional device requires a warm-up time of from four to eight hours prior to use which time is required to enable stabilization of phase shifts in frequency perturbations which are so severe as to render the device useless during the warm-up period;
II. the signal developed by the device exhibits a random phase shift in either direction and the magnitude and occurrence of these phenomena is unpredictable and results in introduction of significant errors into precision timed systems;
III. the minimum time increment resolution is 100 picoseconds which is too coarse (i.e. too large) for the high-stability precision time-keeping systems presently being used; and
IV. when the input clock whose signal is to be time or phase delayed is replaced, there is an accumulated time loss which occurs when one clock is removed from the input jack and another is connected.